Parametric EQ for phone? (seeking solution for hearing imp..

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My wife is hearing impaired and so has great difficulty using a
telephone. Unlike many whose hearing loss is caused by exposure to loud
sounds, her impairment affects the midrange rather than the high
frequencies. Above 5kHz her hearing is only about 5dB down from
baseline...but between 250Hz and 3kHz her hearing is over 70 dB down.

Unfortunately, most of the telephone hardware marketed for hearing
impaired users addresses high frequencies exclusively, or just provides
a global volume boost. In my wife's case, a high frequency boost is
pointless, and a global volume boost can't make enough of an
improvement over her midband attenuation before the upper frequencies
clip or become painfully loud.

So I figured a solution could be just a simple one- or two-band
parametric equalizer tied in to her telephone, so she could dial in a
reciprocal curve to her hearing loss and boost only those frequencies
that are severely attenuated for her.

Question is: how do I connect that equalizer to conventional phone
hardware? I suspect it might involve a hybrid coupler from Gentner or
JK Audio, but it's not immediately obvious to me how to interface the
phone & EQ. Plus I don't want to reinvent the wheel if there's
something already out there that addresses a similar problem.

Any ideas or suggestions? Thanks.

Archived from groups: rec.audio.pro (More info?)

Roscoe East wrote:
> My wife is hearing impaired and so has great difficulty using a
> telephone. Unlike many whose hearing loss is caused by exposure to
loud
> sounds, her impairment affects the midrange rather than the high
> frequencies. Above 5kHz her hearing is only about 5dB down from
> baseline...but between 250Hz and 3kHz her hearing is over 70 dB down.
>

> Any ideas or suggestions? Thanks.

I don't have a solution because the very frequencies that she cannot
hear are the ones that are used in teleonone transmission (200 hz to
3kHz)

A parqametric won't bring anything up enough to make a difference.

About the only thing that could possibly help would be some form of
pitch shifter which would sample the signal and move it a couple of
octaves.

Anybody else have an idea?

Richard Kuschel

Archived from groups: rec.audio.pro (More info?)

"Roscoe East" wrote ...
> My wife is hearing impaired and so has great difficulty using a
> telephone. Unlike many whose hearing loss is caused by exposure to
> loud
> sounds, her impairment affects the midrange rather than the high
> frequencies. Above 5kHz her hearing is only about 5dB down from
> baseline...but between 250Hz and 3kHz her hearing is over 70 dB down.

But 300Hz to 3KHz is exactly the nominal bandpass for telephone
service. Something that bosts telephone volume uniformely would
effectively work only in that bandpass because that is pretty much
all that is there.

Doesn't her hearing aid do this for her?

> Question is: how do I connect that equalizer to conventional phone
> hardware? I suspect it might involve a hybrid coupler from Gentner or
> JK Audio, but it's not immediately obvious to me how to interface the
> phone & EQ. Plus I don't want to reinvent the wheel if there's
> something already out there that addresses a similar problem.

There are four wires going to the handset. Two for the microphone,
and the other two for the earphone. You could physically intercept
the pair that goes to the headphone and run it through almost any
audio equipment.

Lots of pro audio equipment would likely drive the earphone to
"normal" levels. But if you need extra gain, you could add a small
power amp (just a few watts) and drive it as high as the transducer
will allow.